In power and free conveyor systems, it has long been known that the carriers which are movable along a carrier or free track can be disconnected from driving engagement with the conveyor that is movable on the conveyor track by various means. Where the pusher dog is on the carriers and the pusher is on the conveyor, means may be provided on the carrier such that when the carrier engages an obstacle or a preceding carrier, the pusher dog on the carrier is moved out of the path of the pusher on the conveyor. Where the holdback and pusher dogs are pivoted about longitudinally extending axes on the conveyor and the pusher is on the carrier, the problem of accumulation has been approached by providing means long the track for deflecting the pusher and holdback dogs out of the path of the pusher on the carrier. It has also been heretofore suggested that a cam on the carrier be provided for moving the dogs on the conveyor so that they do not engage the pusher on the carrier. However, where the carrier comprises a plurality of trolleys and the pusher is on a trailing trolley, such an arrangement is not suitable.
Accordingly, among the objects of the invention are to provide a system wherein a carrier having a plurality of trolleys with the pusher on a trailing trolley be readily disconnectable from driving engagement with the conveyor upon engagement with an obstacle or a preceding carrier; which system is dependable and which will function effectively upon straight or curved track sections.